Ngā tauira pātai e matapaki ana i ngā Irahiko Kaha, ngā Irahiko Ngoikore, me ngā Irahiko Kore
He ariā taketake ngā irahikohiko i roto i te matū, he mea nui rawa atu, inā koa i roto i te ako i ngā tauhohenga e pā ana ki ngā otinga. Ko ngā irahikohiko he matū e, ina rewa ki te wai, ka puta he iona e āhei ai te otinga ki te kawe hiko. I runga i tō rātou kaha ki te wehewehe hei iona, ka wehea ngā irahikohiko ki ngā wāhanga e toru: ngā irahikohiko kaha, ngā irahikohiko ngoikore, me ngā mea ehara i te irahikohiko. Ka matapakihia e tēnei tuhinga ngā tauira raruraru e pā ana ki ēnei momo irahikohiko e toru, me ngā whakamārama ngāwari ki te mārama.
Irahiko Kaha
Ko ngā irahiko kaha he matū e ionitia katoatia ana i roto i te wai. Ko te tikanga tēnei, ina rewa te irahiko kaha i roto i te wai, ka wehea te nuinga o ōna ngota hei iona. Ko ngā tauira noa o ngā irahiko kaha ko ngā tote pēnei i te konutai pūhaumāota (NaCl), ngā waikawa kaha pēnei i te waikawa hauwaiora (HCl), me ngā kawakore kaha pēnei i te konutai hauwaiora (NaOH).
Pātai 1:
Me pēhea te tatau i te mōraratanga o ngā katote i roto i te otinga HCl 0,1 M?
Kōrero:
He waikawa kaha te HCl e memeha katoa ana i roto i te wai e ai ki te whārite:
\[ \kuputuhi{HCl} \rightarrow \kuputuhi{H}^+ + \kuputuhi{Cl}^- \]
Nā te mea he irahiko kaha te HCl, ka taea te tango i te kukū tīmatanga o te HCl (0,1 M) hei kukū o ngā iona H+ me Cl- i hangaia. Nō reira, i roto i te otinga HCl 0,1 M:
[\(\text{H}^+\)] = 0,1 M
[\(\text{Cl}^-\)] = 0,1 M
Irahiko ngoikore
Ka whaka-ionitihia te iti o ngā irahiko ngoikore i roto i te wairewa. Ko te tikanga he iti noa iho te wāhanga o ngā ngota o te irahiko ngoikore ka hanga i ngā iona ina rewa ki te wai. Ko ngā tauira o ngā irahiko ngoikore ko ngā waikawa ngoikore pērā i te waikawa acetic (CH3COOH) me ngā kawakore ngoikore pērā i te haukini (NH3).
Pātai 2:
Whakatauhia te nui o te ionization me te kukū ion i roto i te 0,1 M CH3COOH. Ko te pūmau wetewete waikawa (\(K_a\)) mō te CH3COOH he 1,8 × 10^-5.
Kōrero:
Ka taea te tuhi i te tauhohenga wehenga o CH3COOH i roto i te wai penei:
\[ \text{CH}_3\text{COOH} \rightleftharpoons \text{CH}_3\text{COO}^- + \text{H}^+ \]
Ko te taumata o te wehenga (\(\alpha\)) e tautuhia ana ko te wāhanga o te waikawa e wehea ana hei iona. Mā te whakamahi i te uara o \(K_a\), ka taea e tātou te tuhi i te whanaungatanga e whai ake nei mō te otinga 0,1 M CH3COOH:
\[ K_a = [\text{CH}_3\text{COO}^-][\text{H}^+] / [\text{CH}_3\text{COOH}] \]
Nā te mea he āputa te ionization o te CH3COOH, ko te kukū o ngā ion i hangaia ko cα, ko c te kukū tīmatanga o te CH3COOH (0,1 M). Kātahi ka pēnei te whārite:
\[ 1,8 \times 10^{-5} = \frac{(0,1\alpha)(0,1\alpha)}{0,1(1-\alpha)} \]
Whakangawaritia kia:
\[ 1,8 \times 10^{-5} = \frac{0,01\alpha^2}{0,1 – 0,1\alpha} \]
Ki tā te whakaaro he iti rawa a α, ā, kāore e taea te wareware i a α i roto i te tauwehenga:
\[ 1,8 \times 10^{-5} \approx 0,01\alpha^2 / 0,1 \]
\[ 1,8 \times 10^{-5} \approx \alpha^2 \]
\[ \alpha \approx \sqrt{1,8 \times 10^{-5}} \]
\[ \alpha \tata ki te 4,24 \times 10^{-3} \]
Nō reira, ko te taumata o te ionization he 4,24 × 10^-3, arā, 0,424%.
Ko te kukū o ngā iona H+ me CH3COO- i roto i te otinga ko:
\[ [\text{H}^+] = 0,1 \times 4,24 \times 10^{-3} \approx 4,24 \times 10^{-4} \]
\[ [\text{CH}_3\text{COO}^-] = 0,1 \times 4,24 \times 10^{-3} \approx 4,24 \times 10^{-4} \]
Ngā kore-irahiko
Ko ngā mea kore-irahiko he matū kāore e ioni i roto i te wairewa. Ko te tikanga, kāore ngā wairewa kore-irahiko e whakaputa i ngā ioni, nō reira kāore e taea te kawe hiko. Ko ngā tauira o ngā mea kore-irahiko ko te huka (sucrose), te urea, me te waipiro.
Pātai 3:
He aha te take kāore e taea ai e te wairewa 0,1 M etanoru (C2H5OH) te kawe hiko?
Kōrero:
He kore-irahiko te otinga etanoru. Ina rewa te etanoru ki te wai, kāore e wehea hei iona. Ka mau tonu te hanganga ngota o te etanoru i roto i te otinga wai. Nā te korenga o ngā iona i roto i te otinga, kāore e taea e te etanoru te kawe hiko. Nō reira, ahakoa he ngāwari te rewa o te etanoru ki te wai, nā te mea kāore he iona e hangaia ana, kāore e taea e ngā otinga etanoru te kawe hiko ahakoa he aha te kukū, tae atu ki te 0,1 M.
Whakamutunga
He tūāpapa nui te mārama ki ngā āhuatanga o ngā irahiko kaha, ngā irahiko ngoikore, me ngā mea ehara i te irahiko i roto i te matū otinga. Ka tino ionize ngā irahiko kaha i roto i te wai, ā, ka pai te kawe hiko, engari ko ngā irahiko ngoikore ka iti noa te ionize, e tohu ana i te iti o te kawe hiko. Ko ngā mea ehara i te irahiko, kāore e ionize, ā, kāore e taea te kawe hiko. Mā te mārama ki tēnei ariā ka āwhina i ngā ākonga ki te tautuhi i ngā matū i runga i ō rātou whanonga i roto i te otinga, me te whakautu tika i ngā pātai e pā ana.
